Processing hydrocarbon oils



Oct. 17, 1939. 2,176,234 P. J. wlezEvlcH, Now BY JUDICIAL CHANGE oF NAME P. J. GAYLoR PROCES S ING HYDROCARBON OILS Filed Oct. 17, 1936 nun: (IU

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Patented Oct. 17, 1939 UNITED STATES PATENT OFFICE judicial change of name Peter 1.*Gaylor, as-

signer to Standard Oil Development Company, a corporation of Dehware Application 0mm 1v, 193s, serial No. 103,155

This invention relates to the processing of hydrocarbon oils to produce motor fuel and pertains more particularly to a combined process for cracking high-boiling hydrocarbons into lower-boiling hydrocarbons within the motor fuel'boiling range, and the reversion of the light normally gaseous hydrocarbons, or hydrocarbons too light for use in motor fuel, into higher-boiling hydrocarbons within the motor fuel boiling range.

The principal object of my invention is to provide a process for converting hydrocarbon oil into gasoline which will materially improve the' yield and quality of motor fuel produced.. A further and more speciiic object of my invention is to reduce the gas loss incident to the cracking process.

In the conversion of hydrocarbon oil into gasoline by conventional pyrolytic and catalytic processes there is formed concurrently with a gasoline, intermediate condensate boiling above the gasoline boiling range amenable to further cracking treatment, heavy residual tarry material unsuitable for cracking and light gaseous hydrocarbons boiling below the normal gasoline boiling range. Since the intermediate condensate is usually returned to the cracking zone and subjected to further cracking, the ultimate gasoline yield is limited by the formation of gases and tar. In many commercial cracking processes the formation of troublesome coke deposits in the cracking zone is the limiting factor determining the extent of cracking. In other processes, particularly the-vapor phase processes operating at high temperature and at relatively low pressure andprocessing light clean condensate, the permissible gas loss is the controlling factor determining the gasoline yield. Expressed in other words, in many high temperature vapor phase cracking operations, the limiting factor is the amount of gas formed rather than the formation of troublesome coke deposits.

Various processes have been developed for revertingor polymerizing these cracked residual gases into higher-boiling hydrocarbons within the gasoline boiling range. Most of these processes involve the separate polymerization of the residual gases, either catalytically or pyrolytically in apparatus separate and distinct from the cracking equipment, although I understand that in some instances it has beeniproposed to return a part of the residual gases to the cracking coil to thermally polymerize such gases concurrently with the cracking of the heavier oil.

In accordance with my invention, the fresh charging oil which may be a gas oil, crude or 4 Claims. (Cl. 196-9) reduced crude, is rst subjected to cracking and the total cracked eniuent, or a vapor fraction thereof enriched with gaseous oleilns is subjected to further treatment which will eect reversion of gases formed during the cracking treatment into higher-boiling hydrocarbons suitable for motor fuel.

The terms reversion of gases and gas reversion as herein employed may be dened as the formation of higher-boiling hydrocarbons from gases whether it result from thecondensation or polymerization of like molecules or by the union of unlike molecules, known as alkylation. Since in my invention the reversion of the gases is in admixture with high-boiling constituents,hit is impossible to determine whether the mechanism by which the gases are caused to unite to form higher-boiling hydrocarbons is one of straight polymerization of like molecules or the alkylation of higher molecular weight hydrocarbons.

A Further, in accordance with my invention,` the vapor products from the reversion zone or the combined reversion and cracking zone, in case the latter is employed as hereinafter described, is separated into a condensate fraction boiling above the range of gasoline, a desired distillate fraction, a saturated gas fraction and an unsaturated gas fraction. The condensate and the saturated gas fraction is then subjected to further cracking either independently or in admixture with the fresh charging oil as circumstances may dictate and the resulting cracked products passed to the reversion .zone hereinbefore described. The unsaturated oleilnic gas fraction is returned directly to the reversion zone where it reacts to form higher-boiling hydrocarbons.

In accordance with the preferred form of my invention, the reversion of the cracked gases is effected in the presence of a polymerizing catalyst. As a catalyst I prefer to employ a volatile metallic halide such as boron and aluminum chloride, although other catalysts such as phosphorus pentoxide, zinc chloride, clay, and phosphoric acid may be used and still retain a number of the advantages of my invention. Boron fluoride is preferred however, since it is more easily recovered and does not form a sludge with the oil.

Other objects and advantages of my invention will be' apparent from the more detailed description hereinafter in which reference will be made to the accompanying drawing which is a diagrammatic illustration of an apparatus suitable for carrying my invention into effect.

Referring to the drawing, the reference character l designates a charging line provided with a pump Ii, which forces the charging oil, which is preferably a. gas oil, but which may be a crude or reduced crude, into the heating coil I2 located in the furnace i3. The oil during its passage through the heating coil I2 is raised to cracking temperature and subjected to cracking therein. 'I'he oil may be heated, for example, to a temperature of from 850 to 1100* F., during its passage through the heating coil I2.

The cracked products from the heating coil I2, pass through transfer line I4 wherein they admix with oleiinic gases introduced through line I5 and the combined products pass to the reaction chamber I6.

In accordance with one mode of operating my proces, the cracked products, enriched* with additional olenic gases are contacted within the reaction chamber I6 with a catalyst capable of` causing gaseous olens to combine to form higher-boiling hydrocarbons. Boron fluoride is particularlysuitable for eifecting such combination, and for convenience and simplicity the speciilc embodiment will be described employing boron iluoride as a catalyst. it being understood that other polymerizing catalysts may be employed.

The catalyst is introduced into the reaction chamber through line I1. The products from the reaction chamber I 6, after undergoing the desired reaction therein, pass through line I3, provided with a reducing valve I9 to a separator 2| wherein the vapors separate from residue. `The unvaporlzed residue is withdrawn'from the separator 2| through line 22 and is rejected from the process. This residue may be subjected to any further treatment desired. The vapors separated in the separator 2| pass overhead through line 23 to a fractionating column 24, wherein insuiilcient- 1y converted constituents are condensed, while the gasoline and lower-boiling constituents are retained in vapor form. 'Ihe insuillciently converted constituents condensed lin fractionating tower 24 are withdrawn therefrom through line 25 and may bewithdrawn from the system through line 26, or part or all of said constituents may be recycled through line 21 provided with pump 23 to theV inlet side of the heating coil I2 and subjected to further cracking therein.

o. vapors remaining uncondensed in the fractionator 24 pass overhead through line 23 to a condenser 3I wherein the gasoline constituents are condensed. The total eminent from the condenser 3i passes to a distillate receiver 32 wherein the gasoline distillate separates from the gases. The gasoline distillate is withdrawn from the receiver 32 through line 33 and may be passed to suitable storage through line 34, but is preferably subjected to further stabilizing treatment. In the latter case, the distillate passes through lines 33 and 35 to a stabilizingzone 35 wherein it is subjected to distillation and fractionation to liberate low-boiling constituents therefrom and produce a stable gasoline. To this end, the stabilizer is suitably heated, such vas by means of a steam coil 31, and is'also provided Vwith fraconating elements 33. The stabilized gasoline is withdrawn from the stabilizer through line 33 and passed to a suitable storage tank (not shown). A portion ofthe stabilized gasoline may be passed through line `4I and after being cooled by passing through heat exchanger 42 introduced into lthe top of the stabilizer as a reilux therefor. The light gases liberated during the stabilizing action pm overhead from the stabilizer 38 through line 43 and is subjected to further treatment for separation of the same into saturates and unsaturates asY hereinafter described.

Returning now to the distillate receiver 32, the gases separated therein pass overhead through line 44 to a hydrolyzer 45, wherein they are treated to separate the boron fluoride therefrom. The gases after being introducedinto the hydrolyzer 45 pass in counter-current contact with a dilute alkali solution, such as sodium hydroxide supplied through a pip'e 50, which reacts with the boron uoride to form a sodium fiuoroborate. This salt solution is withdrawn from the hydrolyzer 45 through line 46 and is passed to a separating chamber 41' wherefrom the boron fluoride is regenerated ina manner well known in the art.

The vapors, after removal of the boron fluoride therefrom in hydrolyzer 45, are passed through line 43 to a solvent extraction zone 43, wherein they are treated with'a selective solvent capable of separating the gases into a rich unsaturated fraction and a lean unsaturated fraction. This separation may be accomplished, for example, by methyl alcohol or other solvents known to selectively dissolve olefines and diolefines from mixed gases. The solvent is introduced into the solvent separator 43 through line 5I and passes countercurrent to the iiow of gases or liquified gases therethrough.

The solvent containing the oleflne or unsaturated constituents is withdrawn from the separator 43 through line 52 and passes to a. distilling chamber 53, wherein it is subjected to distillation to fractionally distill the olenic gases from the solvent. The lean solvent separated in the distilling chamber 53, is removed therefrom through line 54 and is recycled to the top of the solvent separator. Y

'I'he unsaturated gases liberated in the distilling chamber 53 pass overhead through line 55 provided with pump 56 and may be passed via line 51 to the transfer line I 4 where they combine with Aproducts from the cracking coil I2.

Returning now to the solvent separator 43, gases remaining undissolved in the separator pass overhead through line 59 to a hydrogen and methane separating unit, wherein the hydrogen and methane is separated therefrom. 'I'his hydrogen and methane separating unit may comprise anI absorbing column 5I -into which an absorbing medium, such as gas oil, may be introduced into the top through line 52. The gases from the line 53 pass into the bottom of the absorbing tower and pass upwardly therein countercurrent to the downward now of the absorbing medium. The absorber oil selectively absorbs the higher-boiling constituents of the gases and separates the same from hydrogen and methane. The fat absorber ou is withdrawn from the bottom of the absorbing column 5I through line 63 and is passed to a distilling chamber 54, wherein the absorbed gases are distilled therefrom. 'Ihe lean absorber oil from the distilling chamber 64 is withdrawn from the bottom thereof through line 55 which merges with line i2, and is returned to the top of the vabsorbing column 6I. Gases liberated in chamber 54 pass overhead through line, provided with pump 51, and may be recycled to the inlet side of the heating coil I2,

vwherein it is subjected to cracking conditions to form oleiines along with the fresh oil to be' cracked, or a portion or all of the gases may be passed through line 63 to a separate heating coil 3 (which may contain a dehydrogenation or 75 cracking catalyst), located in furnace 1l, and subjected to-separate cracking conditions, pyrolyzing or dehydrogenating the saturated constituents into'a maximum yield of olefines. 'In the 5 latter case, the products from the heating coil i! pass by way of line 'Il to the ,transfer line I4 and are there merged with the cracked products from coil l2.

From the foregoing, it should be evident that, in accordance with my invention, residual gases resulting from the combined cracking and polyo merization unit are separated into saturated and unsaturated constituents. The saturated constituents, after removal 'of hydrogen and methane, are then subjected to cracking for conversion thereof into oleiines, -while the unsaturated constituents of the gases are returned to the transfer line I4 and merged with cracked products therein. The combined products then pass to the reaction m chamber I6 wherein they undergo further reachigher-boiling constituents.y

The reaction chamber Ill may be maintained at a temperature ranging from reforming temperature to active cracking temperature (800-l 1000 F.) and if desired, even above active cracking temperature, such as from 1000 to 1200 F. in which case the reversion of gases and cracking of heavier products takes place concurrently. It is preferred, however, to maintain the reaction chamber at or somewhat below active cracking temperature and preferably between 600-1000 F. The reaction chamber is maintained under superatmospheric pressure ranging from 200-1000 u; lbs/sq. inch. AThe time of contact lwith the catalyst may vary over relatively wide limits from a fraction of a second to fifteen minutes or more depending on the temperature and pressure.

When operating the reaction chamber below active cracking temperature, the cracked products may be cooled either by indirect contact with a cooling-medium in a heat exchanger or the cracked products may be combined with a relatively cold oil preferably a relatively heavy oil. In the drawing, a line 12 is shown merging with transfer .line I4 through which the relatively colder oil may be introduced.

When operating the reaction chamber. li at low temperature, the products therefrom are subjected o to further heating to eifect the desired distillation. The separating chamber 2l is shown provided with a heating coil 12 to eiiect the required heating, it being understood that other types of heating may be employed. l According to another mode of operating my process, `the olefinic gases are charged into the fractionating tower 24 rather than to the reaction chamber I6, so that the gases are rst combined with vapors from cracking operation rather o than with the total cracked products. To this end, a branch line 14 is shown connecting the oleilnic gas line 51 with the bottom of the fractionating tower 24. In such case, the tower 24 serves as a combined fractionatlngand gas reversion zone and the vapor catalyst is contacted with the lighter constituents of the vapors for a materially longer period than with the heavier constituents condensed in the bottom of the fractionating tower. When operating in this manner, -0 a part or all of the catalyst may be introduced into 'the fractionating zone at any one or more of a plurality of spaced points through inlets leading from a common manifold 'l5 so that the catalyst may be caused to contact with any desired portion u of the vapors undergoing fractionation. For exand lmethane all of the gas is ultimately con- 9e tion resulting in the formation of motor fuel and ample, by introducing the catalyst adjacent to the top of the i'ractionating tower only the very lightest fraction of the vapors are caused to contact with the catalyst. In such a case the temperature ofthe oil vapors to be sov treated would 5 bc-in `theni'lighborhod of 40G-800 F., or thereabouts.

When operating the process in this manner, the reaction chamber Il functions principally as a cracking chamber rather than as a gasrever-4 10 sion zone or as a combined cracking and gas reversion chamber although if desired a relatively small amount of catalyst may also be introduced into this chamber.

According to either mode of operating my procw ess, the amount of cracking effected during a single passage 'of the oil through the cracking zone is not limited by the amount of gas loss permissible since with the exception of the hydrogen verted' into higher-boiling constituents. My invention makes it possible to attain an ultimate gasoline, .of high anti-knock gasoline of from 85 to 95% with a .crack per pass based on the 'total oil charge of from 30 to 60 0.

y 'I'he amount of catalyst employed may range from a fraction of a percent, say 0.001 to 0.5% to 10% or more of the oleflne gases introduced to the reversion zone.

For purposes of simplicity, I have in the drawing diagrammatically illustrated only the conventional equipment, it. being understood that other pertinent equipment such as heat exchangers, flow meters, thermostats, etc. will be provided. The process may be operated under a g5 substantially uniform pressure throughout, except for the necessary differential to effect the desired flow hereinbefore described, or a differential pressure between the various portions of the equipment may be maintained. For example, the com- .5@

` bined cracking and polymerization portion of the equipment may be maintained under a relatively high pressure, whereas the hydrolyzer 45 and the solvent separator 49 may be maintained under a materially lower pressure. 4g,

Having described the preferred embodiment, it is understood that my invention embraces such other variations and modifications as come within the spirit and scope thereof and that it is not my intention to unnecessarily limit my invention or to dedicate any novel features thereof.

I claim:

1.v A method of processing hydrocarbon oil which comprises passing a 'stream of oil through a cracking zone and subjecting the same to 55 cracking therein, thereafter separating the cracked products into vapors containing unsaturated gases and residue, fractionating said vapors in a fractionating zone to condense insuiliciently cracked constituents as reflux con- 30 densate, contacting said vapors in said fractionating zone with a catalyst capable of causing said unsaturated gases to react to form higher boiling hydrocarbons, removing vapors remaining uncondensed in said fractionating zone, further gg cooling said vapors to separate the same into a desired distillate fraction and a normally gaseous fraction containing saturatedand unsaturated constituents, separating said gaseous fraction into a saturated component and an unsaturated component and passing said unsaturated component to said fractionating zone.

2. A method of processing hydrocarbon cil which comprises passing a stream'of oil through a cracking zone and subjecting the same to cracking therein, thereafter separating the cracked products into vapors containing unsaturated gases and residue, fractionating said vapors in a fractionating zone to condense insuiiiciently cracked constituents as reflux condensate, contacting said vapors in said fractionating zone with a catalyst capable of causing said unsaturated gases to react to form. higher boiling hydrocarbons, removing vapors remaining uncondensed in said fractionating zone, further cooling said vapors to separate the same into a desired distillate fraction and a normally gaseous fraction containing saturated and unsaturated constituents, separating said gaseous fraction into a saturated component and an unsaturated component. subjecting said saturated component to dehydrogenation to remove hydrogen therefrom and thereby convert said saturated constituents into unsaturated constituents and passing the dehydrogenated component and said unsaturated component to said fractionating zone.

3. A method of processing hydrocarbon oil which comprises passing a stream of oil through a cracking zone and subjecting the same to cracking therein, thereafter separating the cracked products into vapors containing unsaturated gases and residue, fractionating said vapors in a fractionating zone to condense insumciently cracked constituents as reilux condensate, contacting said vapors in said fractionating zone with boron iiuoride to' thereby cause said unsaturated gases to' react to form higher boiling hydrocarbons, removing vapors remaining uncondensed in said fractionating zone, further cooling said vaoprs to separate the same into a desired distillate fraction and a normally gaseous fraction containing saturated and unsaturated hydrocarbon constituents and boron fluoride vapors, separating the boron uoride vapors from said gaseous fraction and returning it to the fractionating zone, separating the remaining gaseous fraction into a saturated component and an olenic component and returning the olenic component to the fractionating zone for 'further treatment therein.

4. A method of processing hydrocarbon oil which comprises passing a stream of oil through a cracking zone and subjecting the same to cracking therein, thereafter separating the cracked products into vapors containing unsaturated gases and residue, fractionating said vapors in a fractionating zone to condense insufficiently cracked constituents as reflux condensate, contacting said vapors in said fractionating zone with boron uoride to thereby cause said unsaturated gases to react to form higher boiling hydrocarbons, removing vapors remaining uncondensed in said fractionating zone, further cooling said vapors to separate the same into a desired distillate fraction and a normally gaseous fraction containing saturated and-unsaturated hydrocarbon constituents and boron uoride vapors, separating the boron fluoride vapors from said gaseous fraction and returning it to the fractionating zone, separating the remaining gaseous fraction into a saturated component and an oleiinic component, dehydrogenating the saturated component of said gaseous fraction to convert the same into unsaturated constituents and passing the dehydrogenated component to the fractionating column for further treatment.

PETER. J. WIEZEVICH. 

